More particularly, the invention relates to an airship intended to fly through the air and to be set down on a solid or liquid surface, comprising:
a flexible envelope with no rigid internal structure and containing a gas lighter than air, said envelope being elongated substantially along a longitudinal axis between a nose situated toward the front of said airship and a tail situated toward the rear of said airship, and comprising an upper part and a lower part, and
a gondola connected to the lower part of the envelope between the nose and the tail.
Numerous examples of airships of this “non-rigid” type, which means of the type having a flexible envelope, are known. Document FR-A-2 628 061 describes one example of such an airship.
With this type of airship, the connection between the gondola and the flexible envelope is not strong enough to lift the gondola. This is because the gas contained in the flexible envelope exerts a lift force which is distributed over the surface of the upper part of the envelope. The gondola is therefore suspended from this upper part of the envelope by cables that pass right through the envelope.
Furthermore, airships of this type need a landing zone comprising a mooring mast aimed at holding the airship near the surface of the ground. Thus, in a crosswind, the airship naturally revolves about the mast like a wind vane until its nose is facing into the wind. These mooring masts are expensive and have to be firmly anchored into the ground.
When such an airship lands, a great many people are needed to stabilize it near the mast, to moor it to the mast by running at least one line between the airship, the top of the mast and the ground in order to bring the nose of the airship up close to the top of the mast, and also around the airship in order to add ballast and assist with stabilizing it near the surface of the ground.
“Rigid” or “semi-rigid”, airships are also known, like those described in U.S. Pat. No. 1,949,304, U.S. Pat. No. 1,350,221, U.S. Pat. No. 2,131,155 or U.S. Pat. No. 2,061,075.
However, these other types of airship are complicated to produce, are heavy and are therefore expensive and inefficient.